Compression molding apparatus

ABSTRACT

A compression molding apparatus equipped with a rotary support member on which are mounted a plurality of molds. The molds are successively conveyed passing through a plastic material feed zone, a compression molding zone and a discharge zone by the rotation of said rotary support member. A plastic material feed device is disposed in said plastic material feed zone to feed a softened and molten plastic material to each of the molds. The plastic material feed device includes an extruder, an extruding block in which a plastic material flow path is formed, and a plastic material flow control device disposed between the extruder and the extruding block. The plastic material flow control device includes a main body that has an inlet path communicating with the extruder, a feed path communicating with the extruding block, and a discard path. The main body includes a control valve which is selectively located at a feed position at which the inlet path is shut off from the discard path and is communicated with the feed path, and at a discard position at which the inlet path is shut off from the feed path and is communicated with the discard path.

TECHNICAL FIELD

The present invention relates to a compression molding apparatus, andparticularly to a compression molding apparatus that can be favorablyadapted to compression-molding a plastic grip ring and simultaneouslylinking it integrally to a linking protruding piece of a containerclosure body.

BACKGROUND ART

Japanese Laid-Open Patent Publication No. 178730/1982 discloses acontainer closure comprised of a metallic container closure body and aplastic grip ring as a suitable example of an easily openable containerclosure. The container closure body is made of a suitable thin metallicplate such as a thin aluminum-base alloy plate and has a circular toppanel wall, a cylindrical skirt wall extending from the peripheral edgeof the circular top panel wall, and a linking protruding pieceprotruding from part of the free end of the skirt wall. The plastic gripring is integrally linked to the linking protruding piece of thecontainer closure body.

Furthermore, Japanese Laid-Open Patent Publication No. 302010/1988discloses a compression molding apparatus which compression-molds aplastic grip ring of a container closure of the above type andsimultaneously links it integrally to a linking protruding piece of acontainer closure body. The above compression molding apparatus isequipped with a compression molding means that includes a rotary supportmember which is rotatably mounted, and a plurality of molds mounted onthe rotary support member maintaining a distance in the circumferentialdirection. As the rotary support member rotates, the molds aresuccessively conveyed via a plastic material feed zone, a containerclosure body feed zone, a compression molding zone and a discharge zone.The compression molding apparatus is further equipped with a plasticmaterial feed means for feeding a heated and molten plastic material toeach of the molds in the plastic material feed zone. The plasticmaterial feed means is constituted by an extruding block having aplastic material flow path formed extending from a receiving port to adischarge port, and an extruder coupled to the extruding block. Thedischarge port of the extruding block is positioned in the plasticmaterial feed zone, and the receiving port of the extruding block iscommunicated with an extruding port of the extruder. The heated andmolten plastic material extruded from the extruder is discharged fromthe discharge port through the plastic material flow path in theextruding block, and is fed to the mold.

The conventional compression molding apparatus involves, however, thefollowing problems that must be solved. The operation of the extruder isstabilized only after some periods of time (e.g., two to three minutes)have passed from the start of its operation in the plastic material feedmeans, and hence, the plastic material extruded from the extruder is notfully adapted to being compression-molded until the above periods oftime have passed. Unacceptable products are produced if the compressionmolding is executed using such an unsuitable resin material. In thecompression molding apparatus of the type mentioned above, furthermore,if the grip ring is compression-molded by feeding the plastic materialunder the condition where the container closure body has not been fed tothe mold in the compression molding means, then the grip ring formedmight be not discharged from the mold but remain therein. That isunacceptable situation. It is therefore desired that the plasticmaterial extruded from the extruder is fed to the mold or is preventedfrom being fed to the mold in accordance with the necessity. However,the conventional compression molding apparatus could not satisfy suchrequirements. It is desired that the extruder is continuously operatedfrom the standpoint of stability in its operation. Therefore, it is notallowed to control the feeding of plastic material by occasionallystopping the operation of the extruder.

DISCLOSURE OF THE INVENTION

The principal object of the present invention is to improve the plasticmaterial feed means of a compression molding apparatus, so that theheated and molten plastic material extruded from the extruder isselectively fed to each of the molds as required without halting theoperation of the extruder.

The gist of the present invention for achieving the above principalobject resides in the arrangement of a plastic material flow controlmeans of a particular form between a extruder in a plastic material feedmeans and an extruding block. Such plastic material flow control meansmust include a main body that has an inlet path communicating with anextruding port of the extruder, a feed path connected with a receivingport of the extruding block and a discard path, as well as a controlvalve that is selectively set at a feed position at which the inlet pathis shut off from the discard path and is connected with the feed pathand at a discard position at which said inlet path is shut off from thefeed path and is connected with the discard path.

According to the present invention, there is provided a compressionmolding apparatus comprising a rotary compression molding means whichincludes a rotary support member that is rotatably mounted, and aplurality of molds mounted on said rotary support member maintaining adistance in the circumferential direction, such that said molds aresuccessively conveyed passing through a plastic material feed zone, acompression molding zone, and a discharge zone by the rotation of saidrotary support member, and a plastic material feed means for feeding aheated and molten plastic material to each of said molds in said plasticmaterial feed zone; wherein

said plastic material feed means includes an extruder, an extrudingblock having a plastic material flow path extending from a receivingport up to a discharge port positioned in said plastic material feedzone, and a plastic material flow control means interposed between saidextruder and said extruding block; and

said plastic material flow control means includes a main body that hasan inlet path communicating with an extruding port of said extruder, afeed path communicating with said receiving port of said extrudingblock, and a discard path, and a control valve that is selectively setat a feed position at which said inlet path is shut off from saiddiscard path and is connected with said feed path and at a discardposition at which said inlet path is shut off from said feed path and isconnected with said discard path.

It is preferable that when the control valve is shifted from the feedposition to the discard position, the inlet path is shut off from thefeed path after said inlet path has been connected with the discardpath, and when the control valve is shifted from the discard position tothe feed position, the inlet path is shut off from the discard pathafter said inlet path has been connected with the feed path.

Desirably furthermore, the main body of said flow control means has acavity of the shape of a truncated cone, and said inlet path, said feedpath and said discard path are connected with said cavity of the shapeof a truncated cone maintaining a predetermined angle, said controlvalve has a valve member of the shape of a truncated cone inserted insaid cavity of the shape of a truncated cone, a communication groove isformed in the outer peripheral surface of said valve member, and whensaid control valve is set at said feed position, the inlet path isconnected with the feed path via said communication groove and when saidcontrol valve is set at said discard position, the inlet path isconnected with the discard path via said communication groove.

According to the compression molding apparatus of the present invention,the control valve in the plastic material flow control means is set atthe discard position when the plastic material should be blocked frombeing fed to the molds in such a case where the operation of theextruder is not stabilized or the container closure body is not fed tothe molds. Then, the plastic material extruded from the extruder iscaused to flow into the discard path from the inlet path of the plasticmaterial flow control means and is blocked from being fed to the molds.The plastic material that flows through the discard path is collected ina suitable collection means and is fed again to the extruder, asrequired. When the plastic material is to be fed to each of the molds,the control valve of the plastic material flow control means ispositioned at the feed position. This enables the plastic materialextruded from the extruding machine to flow into the feed path from theinlet path of the plastic material flow control means, and then to bedischarged from the discharge port flowing through the plastic materialflow path of the extruding block continuing from the feed path so as tobe fed to each of the molds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified lateral sectional view showing a compressionmolding apparatus constructed in accordance with the present inventiontogether with a piercing device;

FIGS. 2-A and 2-B are a perspective and a sectional view of a containerclosure body before being pierced;

FIGS. 3-A and 3-B are a perspective and a sectional view of a containerclosure body pierced by using the piercing device of FIG. 1;

FIGS. 4-A and 4-B are a perspective and a sectional view of a containerclosure that has the container closure body and a plastic grip ringcompression-molded by using the compression molding apparatus of FIG. 1;

FIGS. 5 and 6 are a plan and a side view showing a plastic material feedmeans used for the compression molding apparatus of FIG. 1;

FIGS. 7 and 8 are a plan and a vertical sectional view showing a plasticmaterial flow control means in the plastic material feed means; and

FIGS. 9 and 10 are lateral sectional views showing conditions where thecontrol valve of the plastic material flow control means of FIGS. 7 and8 is at the feed position and at the discard position.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the compression molding apparatus improvedaccording to the present invention will now be described in detail withreference to the accompanying drawings.

FIG. 1 schematically illustrates a container closure-forming systemwhich includes a compression molding apparatus that is generallydesignated at 2 and a piercing device that is generally designated at 4.

The piercing device 4 is constituted by a container closure body feedmeans 6 and a piercing means 8. The container closure body feed means 6in the form of a rotary turret is equipped with a rotary disk 10 that isrotatably mounted to rotate about a center axis that extendssubstantially vertically (perpendicularly to the sheet surface in FIG.1). In the outer peripheral surface of the rotary disk 10 thatcontinuously rotates in a direction indicated by arrow 12 are formed aplurality of container closure body-receiving recesses (not shown) at anequal distance in the circumferential direction. While the rotary disk10 is continuously rotated in a direction indicated by arrow 12, acontainer closure body 18 is fed to each of said receiving recesses froma feed chute 16 in a receiving zone designated at 14. The containerclosure body 18 is conveyed to a feed zone 20 with the turn of therotary disk 10. During this period, the container closure body 18 isprevented from escaping outwardly in the radial direction from thereceiving recess owing to a stationary guide 22 that arcuately extendsfrom the receiving zone 14 to the feed zone 20 along the circumferenceof the rotary disk 10.

The piercing means 8 is equipped with a stationary support shaft 24 thatextends substantially vertically and a rotary support member 26 that isrotatably mounted on the stationary support shaft 24. On the rotarysupport member 26 are arranged a plurality of container closurebody-receiving plates 28 at an equal distance in the circumferentialdirection. Furthermore, a piercing tool assembly (not shown) is arrangedto move up and down over each of the receiving plates 28 on the rotarysupport member 26. In the feed zone 20, the container closure body 18 istransferred from each of the receiving recesses of the rotary disk 10 inthe container closure body feed means 6 to each of the receiving plates28 arranged on the rotary support member 26 of piercing means 8. Therotary support member 26 of the piercing means 8 is continuously rotatedin a direction indicated by arrow 30, and the container closure bodies18 transferred to the receiving plates 28 in the feed zone 20 areconveyed to a discharge zone 32 from the feed zone 20 by the turn of therotary support member 26. During this period, the piercing tool assemblyacts on the container closure body 18 on the receiving plate 28 toperform the required piercing operation. In the discharge zone 32, thecontainer closure body 18 subjected to the required piercing operationis transferred from the piercing means 8 to the compression moldingapparatus 2.

FIGS. 2-A and 2-B illustrate one example of the container closure body18 that is fed from the feed chute 16 to the piercing device 4 or, morespecifically, to the container closure body feed means 6. The containerclosure body 18 may be made of a suitable thin metallic plate such as athin aluminum-base alloy plate, a thin chromate-treated steel plate or athin tin plate, and has a circular top panel wall 34, a cylindricalskirt wall 36 that extending downwardly from the peripheral edge of thetop panel wall 34, and a linking protruding piece 38 that protrudes frompart of the free end of the skirt wall 36. The linking protruding piece38 may protrude from part of the free end of the skirt wall 36 in theaxial direction or in a radial direction and substantially horizontally.Conveniently, however, the linking protruding piece 38 protrudesoutwardly in the radial direction with downward inclination of an angleα which may be about 15 to about 60 degrees as shown. A nearlytriangular notch 37 is formed in the skirt wall 36 on both sides of thebase end of the linking protruding piece 38, and breakable lines 39 areformed extending upwardly from the notches 37. Furthermore, breakablelines 40 (FIG. 2-B) are formed to extend upwardly from the free end ofthe skirt wall 36 at both side portions at an angle of about 90 degreesin the circumferential direction as viewed from the center in thecircumferential direction of the linking protruding piece 38. Thebreakable lines 39 and 40 may be so-called scores. The peripheral edgeof the top panel wall 34 is ridged up, and a plastic annular liner 42 isdisposed on the inside surface of the peripheral ridged edge. As clearlyshown in FIGS. 3-A and 3-B, the linking protruding piece 38 of thecontainer closure body 18 has one or a plurality of (e.g., three) holes44 that are pierced by the piercing means 8 of the piercing device 4.

The above-mentioned piercing device 4 may be constructed as disclosed inJapanese Laid-Open Patent Publication No. 15237/1989 or as disclosed inthe specification and drawings of Japanese Patent Application No.121361/1989 (filed May 17, 1989, entitled "Piercing Device") filed bythe present applicant. As for the details thereof, reference should bemade to the above disclosures, and this specification does not describethem.

The description is continued with reference again to FIG. 1. Thecompression molding apparatus that is generally designated at 2 iscomprised of a rotary compression molding means 46, a container closurebody feed means 48, a discharge means 50, and in addition to these meansa plastic material feed means 52 that is improved in accordance with thepresent invention.

To rotary compression molding means 46 includes a stationary supportshaft 53 that extends substantially vertically (perpendicularly to thesheet surface in FIG. 1) and a rotary support member 54 rotatablymounted on the support shaft 53. On the rotary support member 54 arearranged a plurality of molds 56 (FIG. 1 shows only some of them) thatare arranged on the rotary support member 54 at an equal distance in thecircumferential direction. The rotary support member 54 continuouslyrotates in a direction indicated by arrow 58, so that the molds 56 aresuccessively conveyed through a container closure body feed zone 60, aplastic material feed zone 62, a compression molding zone and adischarge zone 66.

The container closure body feed means 48 may be formed substantially inthe same manner as the container closure body feed means 6 in theaforementioned piercing means 4, and is equipped with a rotary disk 68that is mounted to rotate about a center axis that extends substantiallyvertically. In the outer peripheral surface of the rotary disk 68 thatcontinuously rotates in a direction indicated by arrow 70 are formed aplurality of container closure body-receiving recesses (not shown) at anequal distance in the circumferential direction. While the rotary disk68 continuously rotates in the direction indicated by arrow 70, thecontainer closure bodies 18 that have holes 44 (FIGS. 3-A and 3-B)formed by the piercing means 8 of the aforementioned piercing device 4are discharged from the piercing means 8 in the discharge zone 32 of thepiercing device 4 and are fed to the receiving recesses of the containerclosure body feed means 48 in the compression molding apparatus 2. Thecontainer closure bodies 18 are conveyed to the feed zone 60 by therotation of the rotary disk 68. During this period, the containerclosure bodies 18 are prevented from escaping outwardly in the radialdirection from the receiving recesses owing to the stationary guide 72that extends arcuately along the circumference of the rotary disk 68from the discharge zone 32 up to the feed zone 60. In the feed zone 60,the container closure bodies 18 are transferred from the receivingrecesses of the container closure body feed means 48 to the molds 56 inthe rotary compression molding means 46.

In the plastic material feed zone 62, the heated and molten plasticmaterial is fed to each of the molds 56 in the rotary compressionmolding means 46 by the plastic material feed means 52. The plasticmaterial feed means 52 which is improved in accordance with the presentinvention will be described later in further detail. While the mold 56fed with the container closure body 18 and then with the plasticmaterial is conveyed passing through the compression molding zone 64,the plastic material is compression-molded into a required ring shapeand is linked to the linking protruding piece 38 of the containerclosure body 18. In the discharge zone 66, the container closuresprovided with the plastic ring are discharged into the discharge means50 from the molds 56 of the compression molding means 46. The dischargemeans 50 is constituted by a conveyor belt mechanism including anendless conveyor belt 76 that is driven in a direction indicated byarrow 74. Over the endless conveyor belt 74 is provided a switch lever78 which is selectively positioned at a non-active position indicated bysolid lines and at an active position indicated by two-dot chain lines.As will be described later in detail, when the container closureproduced as desired is discharged onto the endless conveyor belt 76 fromthe mold 56 of the compression molding means 46, the switch lever 78 ispositioned at the non-active position indicated by solid lines. In thiscase, the container closure discharged onto the endless conveyorchecking, counting and packaging regions). On the other hand, when thecontainer closure discharged onto the endless conveyor belt 76 from themold 56 of the compression molding means 46 is an imperfect andunacceptable product, the switch lever 78 is positioned at the activeposition indicated by two-dot chain lines. In this case, the containerclosure discharged onto the endless conveyor belt 76 is not conveyed onthe endless conveyor belt 76 but is introduced into a recovery box 80 bythe action of the switch lever 78.

FIGS. 4-A and 4-B show the container closure having a plastic grip ring82 that is molded as desired by the compression molding means 46. Thegrip ring 82 compression-molded from a suitable plastic material such aspolypropylene or polyethylene has a base portion 84 and a ring-shapedportion 86 that downwardly extends from the base portion 84. The baseportion 84 of the grip ring 82 surrounds the linking protruding piece 38of the container closure body 18 and is integrally linked thereto. Theplastic material from which the grip ring 82 is molded also flows intothe holes 44 formed in the linking protruding piece 38 of the containerclosure body 18 and is cured, so that the grip ring 82 is fully firmlylinked to the linking protruding piece 38.

Here, the rotary compression molding means 6 and the container closurebody feed means 48 in the compression molding apparatus 2 shown in FIG.1 may be those that are disclosed in Japanese Laid-Open PatentPublication No. 302010/1988 or those disclosed in the specification anddrawings of Japanese Patent Application No. 279495/1988 (filed Nov. 7,1968, entitled "Compression Molding Apparatus") filed by the presentapplicant. As for the details thereof, reference should be made to theabove publication and application, and this specification does notdescribe them.

The invention will be further described with reference to FIGS. 5 and 6as well as FIG. 1. The plastic material feed means 52 diagramed in thecompression molding apparatus 2 is constituted by an extruder 90, a gearpump 92, a plastic material flow control means 94 and an extruding block96. An extruder 90 which may be of the known rotary screw type isconnected to the extruding block 96 via the gear pump 92 and plasticmaterial flow control means 94. Similarly, the gear pump 92 which may beof the type known per se feeds the heated and molten plastic materialextruded from the extruder 90 to the plastic material flow control means94 and to the extruding block 96 while suitably compensating thevariation in the amount of the extruded plastic material. The extrudingblock 96 extends substantially horizontally from the plastic materialflow control means 94 up to the plastic material feed zone 62. In theextruding block 96 is formed a plastic material flow path 102 thatextends from a receiving port 98 located at an upstream end thereof to adischarge port 100 located at a downstream end thereof. The dischargeport 100 is opened downwardly in the plastic material feed zone 62. Theheated and molten plastic material downwardly discharged from thedischarge port 100 is cut and separated from the plastic material flowpath 102 of the extruding block 94 by a plastic material receiving unitof the mold that moves passing through the plastic material feed zone 62with the rotation of the rotary disk 68 in the compression molding means46, and thus, is fed to the mold 56 (in this regard, reference should bemade, if necessary, to the specification and drawings of the aboveJapanese Laid-Open Patent Publication No. 302010/1988 or the aboveJapanese Patent Application No. 279495/1988).

If the description is further continued with reference to FIGS. 7 to 10as well as FIG. 1, FIG. 5, FIG. 6, the plastic material flow controlmeans 94 includes a main body 104 secured to a predetermined position bythe clamping bolts arranged at four corner portions and a control valve106 mounted in the main body. As will be clearly understood withreference to FIGS. 7 and 9, a through hole 105 which may have a circularshape in cross section is formed at the central portion of the main body104 in the up-and-down direction. A cylindrical insertion member 107 isinserted in the through hole 105, and a cavity 108 having a shape of atruncated cone is formed by &he inner peripheral surface of theinsertion member 107. In the main body 104 are further formed threepaths, i.e., inlet path 110, feed path 112 and discard path 114 thatstretch radially from the cavity 108 having the shape of a truncatedcone. The inlet path 110 and the feed path 112 are arranged maintainingan angular interval of about 180 degrees relative to each other, and thediscard path 114 is arranged at a position midway between the inlet path110 and the feed path 112. The inlet path 110 is connected to a outletport of the gear pump 92, and the plastic material fed from theextruding machine 90 through the gear pump 92 is caused to flow into theinlet path 110 of the main body 104 in the plastic material flow controlmeans 94. The feed path 112 formed in the main body 104 of the plasticmaterial flow control means 94 is connected to the receiving port 98 ofthe plastic material flow path 102 formed in the extruding block 96. Adischarge pipe 116 is connected to the discard path 114. As will beunderstood with reference to FIGS. 7 and 9, the control valve 106 isconstituted by a valve member 118 having the shape of a truncated conethat corresponds to the cavity 108 having the shape of a truncated coneof the main body 104. The main portion of the valve member 118 havingthe shape of a truncated cone is rotatably accommodated in the cavity108 having the shape of a truncated cone of the main body 104. In theouter peripheral surface of the main portion of the valve member 118having the shape of a truncated cone is formed a communication groove120 extending in the circumferential direction over an angular range ofabout 260 degrees. The valve member 118 having the shape of a truncatedcone has a protruded axle portion 121 of a relatively small diameterthat extends upwardly. The upper end of the protruded axle portion 121upwardly protrudes beyond the upper surface of the main body 104, and islinked to a control valve positioning means 122. A closing member 123 isdisposed to surround the protruded axle portion 121 of the valve member118 having the shape of a truncated cone over the surface of the mainbody 104. The closing member 123 is screwed to the upper end of theinsertion member 107. The control valve positioning means 122selectively positions the valve member 118 having the shape of atruncated cone at the feed position shown in FIG. 9 and at the discardposition shown in FIG. 10. When the valve member 118 having the shape ofa truncated cone is positioned at the feed position shown in FIG. 9, theinlet path 110 and the feed path 112 of the main body 104 arecommunicated with each other via the communication groove 120 of valvemember 118 having the shape of a truncated cone. Consequently, theheated and molten plastic material fed from the extruding machine 90 viagear pump 92 is further conveyed to the plastic material flow path 102of the extruding block 96 via inlet path 110, communication path 120 andfeed path 112, and is discharged from the discharge port 100 of theextruding block 96 so as to be fed to the mold 56 in the compressionmolding means 46. On the other hand, as the valve member 118 having theshape of a truncated cone is positioned at the discard position shown inFIG. 10, the inlet path 110 and the discard path 114 of the main body104 are communicated with each other via the communication groove 120 ofvalve member 118 having the shape of a truncated cone. Consequently, theheated and molten plastic material fed from the extruding machine 90 viagear pump 92 flows passing through the inlet path 110, communicationgroove 120 and discard path 114, and is discharged from the dischargepipe 116. The plastic material discharged from the discharge pipe 116 iscollected on the collection box 124 (FIG. 1). The plastic materialcollected in the collection box 124 can be fed again to the extruder 90,as required. As will be understood from the comparison of FIG. 9 withFIG. 10, when the valve member 118 having the shape of a truncated coneis clockwisely turned in FIG. 9 and is shifted from the feed position tothe discard position, the inlet path 110 is partly communicated with thediscard path 114 via the communication groove 120 and, then, the feedpath 112 is shut off from the communication groove 120, i.e., shut offfrom the inlet path 110. When the valve member 118 having the shape of atruncated cone is counterclockwisely turned in FIG. 10 and is shiftedfrom the discard position to the feed position, the inlet path 110 ispartly communicated with the feed path 112 via the communication groove120 and, then, the discard path 114 is shut off from the communicationgroove 120, i.e., shut off from the inlet path 110. Being constituted asdescribed above, the path of the plastic material flowing through theoutlet port of the gear pump 92 into the inlet path 110 is not closedeven temporarily, making it sure to inhibit formation of considerablyhigh pressure even temporarily on the upstream side of the plasticmaterial flow control means 94 or on the downstream side of the gearpump 92.

If further described with reference to FIGS. 5 and 6, a mounting bracket126 is secured to the casing of the extruder 90. A casing 128 of thecontrol valve positioning means 122 is swingably mounted on the bracket126 by a coupling pin 130. A reversible electric motor 132 is mounted onone end (right end in FIGS. 5 and 6) of the casing 128. The output shaftof the electric motor 132 is coupled to an output shaft 134 via atransmission worm gear mechanism (not shown) equipped inside the casing128. The end of the output shaft 134 slidably mounted in the casing 128is swingably linked to an end of a valve drive member 138 by a couplingpin 136. The other end of the valve drive member 138 is secured to thevalve member 118 having the shape of a truncated cone. Under thecondition shown in FIGS. 5 and 6, when the electric motor 132 isforwardly rotated by a predetermined amount, the output shaft 134stretches out, whereby the valve member 118 having the shape of atruncated cone clockwisely rotates in FIG. 5 and is positioned at thediscard position shown in FIG. 10. When the electric motor 132 isreversely rotated by a predetermined amount under the condition wherethe valve member 118 having the shape of a truncated cone is at thediscard position shown in FIG. 10, the output shaft is contracted to aposition shown in FIG. 5, whereby the valve member 118 having the shapeof a truncated cone is rotated in the counterclockwise direction in FIG.10 and is positioned at the feed position in FIGS. 5 and 9.

The electric motor 132 of the control valve positioning means 122 issuitably rotated forwardly or reversely in relation with stabilizationor the like of the operation of the extruder 90. The valve member 118having the shape of a truncated cone remains located at the discardposition shown in FIG. 10 until a predetermined period of time haspassed after the start of operation of the extruder 90 or, in otherwords, until the operation of the extruder 90 is stabilized and theextruded plastic material acquires the state adapted to beingcompression-molded. Therefore, the plastic material is not fed to themolds 56 in the compression molding means 46. During this period, thecontainer closure body 18 that is fed to the compression molding means46 is discharged from the compression molding means 46 as anunacceptable product that has not plastic grip ring, and is introducedinto the recovery box 80 by the action of the switch lever 78 that islocated at the active position indicated by a two-dot chain line in FIG.1 (reference should also be made to FIGS. 4-A and 4-B in addition toFIG. 1). When the operation of the extruder 90 becomes stabilized, theelectric motor 132 is reversely rotated and the valve member 118 havingthe shape of a truncated cone is located at the feed position shown inFIG. 9. Then, the plastic material starts to be fed to the molds 56 ofthe compression molding means 46, and the container closure body 18 towhich has been coupled the plastic grip ring 46 that has been molded asrequired is discharged from the compression molding means 46. As shownin FIG. 1, a container closure body detecting means 140 is disposed inrelation to the rotary support member 26 of the piercing means 8. Thecontainer closure body detecting means 140 that may be constituted by aphotoelectric detector or the like, detects whether the containerclosure body 18 is present in each of the container closurebody-receiving plates 28 arranged on the rotary support member 26 of thepiercing means 8. When no container closure body 18 exists on thecontainer closure body-receiving plate 28, the valve member 118 havingthe shape of a truncated cone in the plastic material feed means 52 isshifted to the discard position shown in FIG. 10 involving some suitabledelay in time, and the plastic material is interrupted from being fed tothe mold 56 in the compression molding means 46.

Using the compression molding apparatus improved according to thepresent invention, the heated and molten plastic material extruded fromthe extruding machine can be selectively fed to the molds in thecompression molding means by suitably operating the plastic materialflow control means without stopping the operation of the extrudingmachine. Therefore, it is made possible to reliably prevent unexpectedproduction of unacceptable products and to prevent the plastic materialfrom remaining in the molds that must be avoided by all means.

We claim:
 1. A compression molding apparatus comprising a rotarycompression molding means which includes a rotary support member that isrotatably mounted, and a plurality of molds mounted on said rotarysupport member maintaining a distance in the circumferential direction,such that said molds are successively conveyed passing through a plasticmaterial feed zone, a compression molding zone, and a discharge zone bythe rotation of said rotary support member, and a plastic material feedmeans for feeding a heated and molten plastic material to each of saidmolds in said plastic material feed zone; whereinsaid plastic materialfeed means includes an extruder, an extruding block having a plasticmaterial flow path extending from a receiving port up to a dischargeport positioned in said plastic material feed zone, and a plasticmaterial flow control means interposed between said extruder and saidextruding block; and said plastic material flow control means includes amain body that has an inlet path communicating with an extruding port ofsaid extruder, a feed path communicated with said receiving port of saidextruding block, and a discard path, and a control valve that isselectively set at a feed position at which said inlet path is shut offfrom said discard path and is connected with said feed path and at adiscard position at which said inlet path is shut off from said feedpath and is connected with said discard path.
 2. A compression moldingapparatus according to claim 1, wherein when said control valve isshifted from said feed position to said discard position, said inletpath is shut off from said feed path after said inlet path has beenconnected with said discard path, and when said control valve is shiftedfrom said discard position to said feed position, said inlet path isshut off from said discard path after said inlet path has been connectedwith said feed path.
 3. A compression molding apparatus according toclaim 1, wherein said main body of said flow control means has a cavityof the shape of a truncated cone, and said inlet path, said feed pathand said discard path are connected with said cavity of the shape of atruncated cone maintaining a predetermined angle, said control valve hasa valve member of the shape of a truncated cone inserted in said cavityof the shape of a circular truncated cone, a communication groove isformed in the outer peripheral surface of said valve member, and whensaid control valve is set at said feed position, said inlet path isconnected with said feed path via said communication groove and whensaid control valve is set at said discard position, said inlet path isconnected with said discard path via said communication groove.
 4. Acompression molding apparatus according to claim 1, wherein said plasticmaterial flow control means includes a control valve positioning meanswhich selectively positions said control valve at said feed position orat said discard position.
 5. A compression molding apparatus accordingto claim 4, wherein said control valve positioning means is constitutedby an electric motor.
 6. A compression molding apparatus according toclaim 1, wherein said plastic material feed means includes a gear pumpthat is interposed between said extruder and said plastic material flowcontrol means.
 7. A compression molding apparatus according to claim 1,wherein a container closure body feed zone exists on the downstream sideof said discharge zone but on the upstream side of said compression zoneas viewed in a direction in which said rotary member rotates, acontainer closure body feed means is disposed in said container closurebody feed zone to feed to each of said molds a container closure bodythat has a circular top panel wall, a cylindrical skirt wall extendingfrom the peripheral edge of said top panel wall and a linking protrudingpiece that protrudes from part of the free end of said skirt wall, and aplastic grip ring is compression-molded in said molding zone and issimultaneously integrally linked to said linking protruding piece ofsaid container closure body.